Antidrip agents for thermoplastic molding compounds

ABSTRACT

Halogen-free antidrip agents for thermoplastic molding materials contain polymers based on vinylaromatic monomers and having molecular weights (M w ) of at least 800 000 g/mol and a narrow molecular weight distribution.

The present invention relates to antidrip agents for thermoplasticmolding materials which contain polymers which are based onvinylaromatic monomers and have molecular weights (M_(w)) of at least800 000 g/mol and a narrow molecular weight distribution. Preferredembodiments are described in the subclaims and the description.

When thermoplastic materials are ignited, they generally soften veryrapidly (unless crosslinking reactions occur) since their viscositydecreases markedly owing to the high temperatures. Frequently,therefore, particles of the material separate off from the molding. Thisprocess is referred to as dripping or, if the sample is still burning,as the dripping of flaming particles. Dripping material particles canreadily ignite other articles and thus propagate a fire. Considerableefforts have therefore been made to develop effective antidrip agentsfor thermoplastic molding materials.

Although halogen-containing polymers, such as polytetrafluoroethylenes,counteract dripping, they should be avoided for reasons of environmentalcompatibility. EP-A-550 204 describes high molecular weightpolyethylenes as halogen-free antidrip agents for thermoplastic moldingmaterials comprising polyphenylene ethers and high impact polystyrenes(HIPS). However, it has been found that even small amounts of highmolecular weight polyethylene adversely affect the mechanical propertiesof precisely these molding materials. In particular, the damaging energydecreases dramatically. EP-A-305 764 recommends polystyrenes havingmolecular weights of more than 400 000 g/mol and a broad molecularweight distribution as antidrip agents for blends of polyphenyleneethers and HIPS. On the one hand, these antidrip agents do notsufficiently decrease the tendency of the thermoplastic moldingmaterials to drip and, on the other hand, they increase the meltviscosity at the shear rates relevant to processing by injectionmolding. Furthermore, the toughness of the molding materials is reducedas the proportion of antidrip agent increases.

That blends of polyphenylene ethers and HIPS may additionally containpolystyrenes is furthermore disclosed, for example, in U.S. Pat. No.4,128,602, 4,128,603 and 5,008,314 and EP-A-476 366. The moldingmaterials described in U.S. Pat. No. 5,008,314 have improved stresscracking resistances and those of EP-A-476 366 are particularly suitablefor blow molding.

It is an object of the present invention to provide novel effectivehalogen-free antidrip agents for thermoplastic molding materials, inparticular for polyphenylene ether/HIPS blends, which have very littleeffect on the mechanical properties of the blends.

We have found that this object is achieved by the antidrip agentsdefined at the outset.

The polymers contained in the novel halogen-free antidrip agents andbased on vinylaromatic monomers may be both homopolymers and randomcopolymers or block copolymers, such as alternating block copolymers,star block copolymers or three-block or five-block copolymers. Blends ofdifferent polymers are also suitable. Homopolymers are preferably used.The polymers based on vinylaromatic monomers may be either syndiotacticor atactic. In general, however, atactic polymers based on vinylaromaticmonomers are used.

Suitable vinylaromatic monomers have, as a rule, 8 to 12 carbon atoms.Styrene or styrenes substituted in the nucleus or in the side chain areparticularly suitable. Examples are o-methylstyrene, m-methylstyrene,p-methylstyrene and p-tert-butylstyrene.

Other monomers may also be present, in particular those which arecapable of anionic copolymerization with the stated monomers. Theseinclude acrylonitrile, methacrylonitrile, 2-vinylpyridine,4-vinylpyridine and vinylpyrrolidone.

Very particularly preferred novel antidrip agents contain polystyrenehomopolymers.

According to the invention, the polymers based on vinylaromatic 35monomers have weight average molecular weights (M_(w)) of at least 800000, for example 900 000, g/mol or more. In general, the molecularweights (M_(w)) are from 800 000 to 2.8×10⁶, preferably from 1×10⁶ to2.5×10⁶, g/mol. In general, polymers based on vinylaromatic monomers andhaving molecular weights (M_(w)) of more than 3×10⁶ g/mol are difficultto prepare and are therefore not preferred. In a particularly preferredembodiment, the molecular weights (M_(w)) are from 1.1×10⁶ to 2.3×10⁶,in particular from 1.2×10⁶ to 2.2×10⁶, g/mol. The novel antidrip agentscan be used in various thermoplastic molding materials. It isparticularly advantageous to use the novel antidrip agents inthermoplastic molding materials which are compatible with the novelantidrip agents. This means that the novel antidrip agents arepreferably miscible with the matrix of the thermoplastic moldingmaterial or can be readily dispersed therein.

According to the invention, the polymers based on vinylaromatic monomershave a narrow molecular weight distribution, ie. the ratio of weightaverage to number average molecular weights M_(w) /M_(n) is small. Theratio M_(w) /M_(n) is preferably 2.5 or less. M_(w) /M_(n) isparticularly preferably 2 or less, for example less than 1.8.

The polymers based on vinylaromatic monomers which are contained in thenovel antidrip agents are preferably prepared by anionic polymerization.Anionic emulsion polymerization is particularly preferred.

Anionic polymerization methods are known per se. In general, thepolymerization is carried out in the presence of stoichiometric amountsof organic lithium compounds, preferably alkyllithium compounds, inparticular n-butyllithium, sec-butyllithium or tert-butyllithium.

In the anionic emulsion polymerization, the reaction is carried out as arule in an inert solvent in which the polymer is insoluble. The reactionmay also be effected in a solvent mixture comprising short-chain andlong-chain aliphatic hydrocarbons.

The suitable solvents include butane, isobutane, pentane, isopentane,hexane, heptane, 2,2-dimethylbutane, petroleum ether and cyclohexane.These may be used as a mixture with hydrocarbons which are of 14 carbonatoms or more, including tetradecane, hexadecane, octadecane oreicosane, and liquid oligomers of olefins, such as ethylene or higherolefins of 3 to 12 carbon atoms, such as decene.

Solid oligomers of the stated olefins or polystyrenes or polysiloxaneshaving a low molecular weight may also be used as cosolvents.

The reaction can also be carried out in the presence of polymericdispersants which keep the resulting polymer in suspension. Examples ofsuitable dispersants are copolymers of styrene and butadiene, isopreneor hydrogenated isoprenes.

Very particularly preferably, pentane is used as the solvent andstyrene/butadiene block copolymers as dispersants.

Suitable styrene/butadiene block copolymers are, for example, two-blockcopolymers of the type a-b, where a is a polymer block of styrene and bis a polymer block of butadiene, preferably 1,4-polybutadiene. The sumof the components a and b is 100% by weight, and the composition of aand b may vary. Thus, a may be from 10 to 90% by weight and accordinglyb from 90 to 10% by weight, but a is preferably from 20 to 80% by weightand b from 80 to 20% by weight.

For example, the commercial products ®Nippon NS 312, ®Buna KA 8497,®Kraton G 1701X and ®Septon 1001 are suitable.

A particularly suitable styrene/butadiene block copolymer is, forexample, a styrene/butadiene two-block copolymer which may behydrogenated and which is used in an amount of, for example, from 1 to10% by weight, based on the vinylaromatic monomer. It is advantageouslyadded in the form of a solution in the monomer to the emulsion to bepolymerized.

Compounds which promote the tendency toward a random distribution may bepresent in the preparation of random copolymers. Such compounds are, forexample, tetrahydrofuran, tetramethylethylenediamine, potassium amylateand tert-butyl phosphate.

The polymerization process is generally carried out at from 0 to 100° C.Preferred reaction temperatures are from 0 to 30° C. The reaction can becarried out both at atmospheric pressure and at superatmosphericpressure.

It is generally sufficient if the antidrip agents are contained in smallamounts, for example from about 0.5 to 25% by weight, based on the totalcomposition, in the thermoplastic molding materials. Preferredcompositions of thermoplastic molding materials and antidrip agentscontain from 1 to 20, in particular from 1 to 15, % by weight ofantidrip agents.

The novel antidrip agents are preferably used in compositions whichcontain polyphenylene ethers and vinylaromatic polymers.

Particularly preferred compositions are those which contain

A) from 0.5 to 25% by weight of an antidrip agent as claimed in any ofclaims 1 to 4,

B) from 5 to 97.5% by weight of polyphenylene ether,

C) from 1 to 93.5% by weight of vinylaromatic polymers which differ fromthe polymers contained in the antidrip agent,

D) from 0 to 50% by weight of impact modifiers,

E) from 1 to 20% by weight of flameproofing agents and

F) from 0 to 60% by weight of additives or processing assistants or ofmixtures thereof.

Component A

According to the invention, the novel antidrip agents are contained inthe compositions as component A in an amount of from 0.5 to 25,preferably from 0.5 to 15, in particular from 0.5 to 10, % by weight,based on the total composition.

Component B

According to the invention, the polyphenylene ethers B are contained inthe compositions in an amount of from 5 to 97.5, preferably from 10 to93.5, in particular from 15 to 88.5, % by weight, based on the totalcomposition.

The polyphenylene ethers B are known per se. They are compounds based onsubstituted, in particular disubstituted, polyphenylene ethers, theether oxygen of one unit being bonded to the benzene nucleus of theneighboring unit. Polyphenylene ethers substituted in the 2- and/or6-position relative to the oxygen atom are preferably used. Examples ofsubstituents are halogen, such as chlorine or bromine, and alkyl of 1 to4 carbon atoms which preferably has no α tertiary hydrogen atom, forexample methyl, ethyl, propyl or butyl. The alkyl radicals in turn maybe substituted by halogen, such as chlorine or bromine, or by hydroxyl.Further examples of possible substituents are alkoxy, preferably of upto 4 carbon atoms, or phenyl which is unsubstituted or substituted byhalogen and/or alkyl. Copolymers of different phenols, for examplecopolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol, are alsosuitable. Mixtures of different polyphenylene ethers can of course alsobe used.

Examples of polyphenylene ethers B are

poly(2,6-dilauryl-1,4-phenylene ether),

poly(2,6-diphenyl-1,4-phenylene ether),

poly(2,6-dimethoxy-1,4-phenylene ether),

poly(2,6-diethoxy-1,4-phenylene ether),

poly(2-methoxy-6-ethoxy-1,4-phenylene ether),

poly(2-ethyl-6-stearyloxy-1,4-phenylene ether),

poly(2,6-dichloro-1,4-phenylene ether),

poly(2-methyl-6-phenyl-1,4-phenylene ether),

poly(2,6-dibenzyl-1,4-phenylene ether),

poly(2-ethoxy-1,4-phenylene ether),

poly(2-chloro-1,4-phenylene ether) and

poly(2,5-dibromo-1,4-phenylene ether).

Polyphenylene ethers in which the substituents are alkyl of 1 to 4carbon atoms, such as

poly(2,6-dimethyl-1,4-phenylene ether),

poly(2,6-diethyl-1,4-phenylene ether),

poly(2-methyl-6-ethyl-1,4-phenylene ether),

poly(2-methyl-6-propyl-1,4-phenylene ether),

poly(2,6-dipropyl-1,4-phenylene ether) and

poly(2-ethyl-6-propyl-1,4-phenylene ether), are preferably used.

For the purposes of the present invention, polyphenylene ethers are alsoto be understood as meaning those which are modified with monomers suchas fumaric acid, maleic acid or maleic anhydride.

Such polyphenylene ethers are described, inter alia, in WO 87/00540.

With regard to the physical properties of the polyphenylene ethers,those which have a weight average molecular weight M_(w) of from 8 000to 70 000, preferably from 12 000 to 50 000, in particular from 20 000to 45 000, are used in the compositions.

This corresponds to a limiting viscosity of from 0.18 to 0.7, preferablyfrom 0.25 to 0.55, in particular from 0.30 to 0.50, dl/g, measured inchloroform at 25° C.

The molecular weight distribution is determined in general by means ofgel permeation chromatography (Shodex separation columns 0.8×50 cm ofthe types A 803, A 804 and A 805, with tetrahydrofuran as eluent at roomtemperature). The polyphenylene ether samples are dissolved intetrahydrofuran under pressure at 110° C., 0.16 ml of a 0.25% strengthby weight solution being injected.

Detection was effected in general by means of a UV detector. Thecalibration of the columns was carried out with polyphenylene ethersamples whose absolute molecular weight distributions were determined bya GPC/laser light scattering combination.

Component C

According to the invention, component C is contained in the compositionsin amounts of from 1 to 93.5, preferably from 5 to 88.5, in particularfrom 10 to 83.5, % by weight, based on the total weight of thecomposition.

Component C comprises vinylaromatic polymers which are preferablycompatible with the polyphenylene ether used. The vinylaromatic polymersC differ from the polymers contained in the antidrip agent.

Both homopolymers and copolymers of vinylaromatic monomers of 8 to 12carbon atoms, which are prepared in the presence of a rubber, aresuitable. The rubber content is from 5 to 25, preferably from 8 to 17, %by weight.

High impact polystyrenes or copolymers of styrene and othervinylaromatic compounds are particularly suitable. Such high impactpolystyrenes are generally referred to as HIPS and for the most part arecommercially available and have a viscosity number (VN) of the hardmatrix of from 50 to 130, preferably from 60 to 90, ml/g (0.5% strengthin toluene at 23° C.).

Suitable monovinylaromatic compounds are styrenes alkylated in thenucleus or in the side chain. Examples are chlorostyrene,α-methylstyrene, p-methylstyrene, vinyltoluene and p-tert-butylstyrene.However, styrene alone is preferably used.

The homopolymers are generally prepared by the known mass, solution orsuspension polymerization methods (cf. Ullmanns Enzyklopadie der techn.Chemie, Volume 19, pages 265 to 272, Verlag Chemie, Weinheim 1980). Thehomopolymers may have weight average molecular weights M_(w) of from 3000 to 300 000, which can be determined by conventional methods.

Examples of suitable comonomers for the preparation of copolymers are(meth)acrylic acid, alkyl (meth)acrylates where the alkyl radical is of1 to 4 carbon atoms, acrylonitrile and maleic anhydride and maleimides,acrylamide and methacrylamides and their N,N- or N-alkyl-substitutedderivatives where the alkyl radical is of 1 to 10 carbon atoms.

Depending on their chemical structure, the comonomers are present invarying amounts in the styrene polymers. The miscibility of thecopolymer with the polyphenylene ether is decisive with regard to thecontent of comonomers in the copolymer. Such mixing limits are known andare described, for example, in U.S. Pat. Nos. 4,360,618 and 4,405,753and in the publication by J. R. Fried and G. A. Hanna, Polymer Eng. Sci.22 (1982), 705 et seq.. The copolymers are prepared by known methods,which are described, for example, in Ullmanns Enzyklopadie der techn.Chemie, Volume 19, page 273 et seq., Verlag Chemie, Weinheim (1980). Thecopolymers generally have a weight average molecular weight (M_(w)) offrom 10 000 to 300 000, which can be determined by conventional methods.

Component C is preferably high impact polystyrene.

The generally used processes for the preparation of toughened styrenepolymers are mass and solution polymerization in the presence of arubber, as described, for example, in U.S. Pat. No. 2,694,692, andmass-suspension polymerization processes, as described, for example, inU.S. Pat. No. 2,862,906. Other processes can of course also be used,provided that the rubber phase is brought to the desired particle size.

Component D

According to the invention, the impact modifiers D are contained in thecompositions in an amount of from 0 to 50% by weight, based on the totalcomposition. Preferred compositions contain from 0 to 40, in particularfrom 0 to 20, % by weight of component D.

Natural or synthetic rubbers may be used as component D. In addition tonatural rubber, other suitable impact modifiers are, for example,polybutadiene, polyisoprene or copolymers of butadiene and/or ofisoprene with styrene and other comonomers, which have a glasstransition temperature of less than -20° C., determined according to K.H. Illers and H. Breuer, Kolloidzeitschrift 190 (1) (1963), 16-34.

Preferred impact modifiers D are block copolymers of vinylaromatics anddienes, which are distinguished by the fact that a soft block comprisingdiene and vinylaromatic is present instead of a pure diene rubber, dieneand vinylaromatic being randomly distributed in the soft block.

Preferred vinylaromatics are styrene, α-methylstyrene, vinyltoluene andmixtures of these compounds. Preferred dienes are butadiene, isoprene,piperylene, 1-phenylbutadiene or mixtures of these compounds. Aparticularly preferred monomer combination is butadiene and styrene.

The soft blocks are particularly preferably composed of from 31 to 75%by weight of styrene and from 25 to 69% by weight of butadiene. Softblocks which have a butadiene content of from 34 to 69% by weight and astyrene content of from 31 to 66% by weight are very particularlypreferred.

Block copolymers comprising styrene and butadiene and having a monomercomposition of from 15 to 66, in particular from 25 to 62, % by weightof diene and from 34 to 85, in particular from 38 to 75, % by weight ofvinylaromatic are particularly preferred.

The proportion by volume of the soft block in the solid block copolymeris in general from 60 to 95, preferably from 70 to 90, in particularfrom 80 to 88, % by volume. The proportions by volume of the hard phaseformed from the vinylaromatics is accordingly from 5 to 40, preferablyfrom 10 to 30, in particular from 12 to 20, % by volume.

The block copolymers are unambiguously defined by the quotient of theproportion by volume of the soft blocks and the percentage by weight ofdiene in the soft blocks. In addition, the block copolymers are, as arule, characterized by glass transition temperatures of from -50 to +25°C., in particular from -50 to +5° C.

The composition of the block copolymers may be on average homogeneous orinhomogeneous along the chain. The chain structure of the blockcopolymers may be linear or star-like. The composition can be described,for example, by the following general formulae:

    (V-Q/V).sub.n

    (V-Q/V).sub.n -V

    Q/V-(V-Q/V).sub.n

    x.brket open-st.(V-Q/V).sub.n ].sub.m+1

    x.brket open-st.(Q/V-V).sub.n ].sub.m+1

    x.brket open-st.(V-Q/V).sub.n -V].sub.m+1

    x.brket open-st.(Q/V-V).sub.n -Q/V].sub.m+1

    y.brket open-st.(V-Q/V).sub.n ].sub.m+1

    y.brket open-st.(Q/V-V).sub.n ].sub.m+1

    y.brket open-st.(V-Q/V).sub.n -V].sub.m+1

    y.brket open-st.(Q/V-V).sub.n -Q/V].sub.m+1

In these formulae, V is a hard phase comprising vinylaromatics,Q/V_(m+1) is a soft block, X is a bifunctional or polyfunctionalinitiator and Y is a coupling center formed with a bifunctional orpolyfunctional coupling agent. m and n are each an integer, beginningwith one.

Preferred block copolymers have the structure V-Q/V-V, X-[Q/V-V]₂ orY-[Q/V-V]₂, where the soft block Q/V itself may be subdivided intopart-blocks. The soft block preferably consists of from 2 to 15, inparticular from 3 to 10, random part-blocks.

The block copolymers may be prepared by living anionic polymerization innonpolar solvents with the addition of polar cosolvents acting as Lewisbases. Preferably used solvents are aliphatic hydrocarbons, such ascyclohexane or methylcyclohexane. Suitable cosolvents are ethers, suchas tetrahydrofuran, or aliphatic polyethers, eg. diethylene glycoldimethyl ether, or tertiary amines, such as tributylamine or pyridine.

Examples of initiators for the anionic polymerization are organometalliccompounds, including methyllithium, ethyllithium, n-propyllithium,n-butyllithium, sec-butyllithium or tert-butyllithium.

The coupling center Y is formed by the reaction of the reactive anionicchain ends with a bifunctional or polyfunctional coupling agent. Suchcoupling agents are known per se. Divinylbenzene or epoxidized glycides,such as epoxidized linseed oil or soya bean oil, are preferred.

The anionic polymerization is carried out in a plurality of stages. Apart of the monomers is initially taken in the reactor and the anionicpolymerization is initiated by adding the initiator. In order to achievea defined chain structure which can be calculated from the metering ofthe monomer and of the initiator, it is advisable to allow the reactionto proceed to high conversions (≧99%) before the second monomer isadded. However, this is not absolutely essential. The order of themonomer addition depends on the chosen block structure. In the case ofmonofunctional initiation, first vinylaromatic is either initially takenor directly metered in. Thereafter, diene and vinylaromatic should beadded as far as possible simultaneously. The random structure and thecomposition of the soft block Q/V are determined by the metering ofdiene relative to vinylaromatic compound, the concentration and thechemical structure of the Lewis base as well as the reactiontemperature. Thereafter, either the second hard phase V is polymerizedby adding the vinylaromatic or coupling is effected with a couplingagent. In the case of bifunctional initiation, the soft block Q/V isfirst synthesized, followed by the hard phase V.

The block copolymers can be worked up by protonating the carbanions withan alcohol, such as isopropanol, acidifying the reaction mixture, forexample with a mixture of CO₂ and water, and removing the solvent. Theblock copolymers may contain antioxidants and antiblocking agents.

Component E

The compositions contain, as component E, flameproofing agents inamounts of from 1 to 20, preferably from 1 to 18, in particular from 1to 15, % by weight, based on the total composition.

Organophosphorus compounds, such as phosphates or phosphine oxides, maybe used as flameproofing agents. Examples of phosphine oxides ortriphenylphosphine oxide, tritolylphosphine oxide,trisnonylphenylphosphine oxide, tricyclohexylphosphine oxide,tris(n-butyl)phosphine oxide, tris(n-hexyl)phosphine oxide,tris(n-octyl)phosphine oxide, tris(cyanoethyl)phosphine oxide,benzylbis(cyclohexyl)phosphine oxide, benzylbisphenylphosphine oxide andphenylbis(n-hexyl)phosphine oxide. Triphenylphosphine oxide,tricyclohexylphosphine oxide, tris(n-octyl)phosphine oxide andtris(cyanoethyl)phosphine oxide are particularly preferably used.

Particularly suitable phosphates are alkyl- and aryl-substitutedphosphates. Examples are phenyl bisdodecyl phosphate, phenylbisneopentyl phosphate, phenyl ethyl hydrogen phosphate, phenylbis(3,5,5-trimethylhexyl)phosphate, ethyl diphenyl phosphate,bis(2-ethylhexyl)p-tolyl phosphate, tritolyl phosphate, trixylylphosphate, trimesityl phosphate, bis(2-ethylhexyl)phenyl phosphate,tris(nonylphenyl)phosphate, bisdodecyl p-tolyl phosphate, tricresylphosphate, triphenyl phosphate, dibutyl phenyl phosphate, p-tolylbis(2,5,5-trimethylhexyl)phosphate and 2-ethylhexyl diphenyl phosphate.Phosphorus compounds in which each radical R is aryl are particularlysuitable. Triphenyl phosphate, trixylyl phosphate and trimesitylphosphate are very particularly suitable. Cyclic phosphates may also beused. Diphenyl pentaerythritol diphosphate is particularly suitablehere.

In addition, mixtures of different phosphorus compounds may be used. Forexample, mixtures which are composed of

α) at least one phosphine oxide of the general formula I ##STR1## whereR¹, R² and R³ are identical or different alkyl, aryl, alkylaryl orcycloalkyl groups of 8 to 40 carbon atoms, and

β) at least one phosphate of the general formula II ##STR2## where R⁴,R⁵ and R⁶ are identical or different alkyl, aryl, alkylaryl orcycloalkyl groups of 8 to 40 carbon atoms,

and

γ) a boron compound

are preferred.

Mixtures of the following phosphine oxide α) and phosphate β)combinations are particularly preferred: triphenylphosphineoxide/triphenyl phosphate or trixylyl phosphate, tricyclohexylphosphineoxide and triphenyl phosphate, tris(cyanoethyl)phosphine oxide andtriphenyl phosphate, tris(n-octyl)phosphine oxide and triphenylphosphate. Mixtures of a plurality of phosphine oxides and phosphatesmay also be used, for example a mixture of triphenylphosphine oxide,triphenyl phosphate and trixylyl phosphate.

Boron compounds γ) are to be understood as meaning both inorganic andorganic boron compounds.

Examples of inorganic boron compounds are boric acid, B₂ O₃ and salts ofboric acid, preferably with alkali or alkaline earth metals. Boric acid,sodium borate and boron oxide are particularly preferred.

Organic boron compounds γ) are, for example, tetraphenylborates, eg.sodium tetraphenylborate and tribenzyl borate.

The composition of the mixture is in general (based on the content ofthe total mixture)

α) from 1 to 98.9, preferably from 10 to 85, in particular from to 70, %by weight,

β) from 1 to 98.9, preferably from 10 to 85, in particular from to 70, %by weight and

γ) from 0.1 to 70, preferably from 5 to 50, in particular from 10 to 30,% by weight.

Organophosphorus compounds of the general formulae III to V ##STR3##where R⁷ and R¹¹ are each alkyl or aryl, R⁸, R¹⁰, R¹² and R¹³ are eachalkyl, aryl, alkoxy or aryloxy, n and p are each an integer from 1 to30, R⁹ is alkyl, --SO₂ --, --CO--, --N═N-- or R¹⁴ --P═O and R¹⁴ isalkyl, aryl or alkylaryl, are also suitable flameproofing agents.

In general, mixtures of different oligomers or isomers of theseorganophosphorus compounds are used.

The molecular weight is in general not more than 1 000, preferably from150 to 800.

Component F

The compositions may contain, as component F, additives or processingassistants or mixtures thereof. The amount of component F is in generalfrom 0 to 60% by weight, based on the total composition. It ispreferably not more than 50, in particular not more than 30, % byweight, based on the total composition.

Examples of additives are heat stabilizers and light stabilizers,lubricants and mold release agents, and colorants, such as dyes andpigments, in conventional amounts. Further additives are reinforcingagents, such as glass fibers, carbon fibers, aromatic polyamide fibersand/or fillers, gypsum fibers, synthetic calcium silicates, kaolin,calcined kaolin, wollastonite, talc and chalk.

Lubricants, such as polyethylene wax, are also suitable as additives.

Carbon blacks and titanium dioxide may be used, for example, aspigments.

When TiO₂ is used, the mean particle size is as a rule from 50 to 400nm, in particular from 150 to 240 nm. Rutile and anatase, which may becoated with metal oxides, eg. aluminas, silicas, oxides of zinc orsiloxanes, are used industrially.

Carbon blacks are to be understood as meaning microcrystalline, finelydivided carbons (cf. Kunststofflexikon, 7th Edition 1980).

Furnace blacks, acetylene blacks, gas blacks and the thermal carbonblacks obtainable by thermal preparation are suitable examples.

The particle sizes are preferably from 0.01 to 0.1 μm and the surfaceareas are from 10² to 10⁴ m² /g (BET/ASTM D 3037), in the case of DBPabsorption from 10² to 10³ ml/100 g (ASTM D 2414).

The novel thermoplastic molding materials are advantageously prepared bymixing the components at from 250 to 320° C. in a conventional mixingapparatus, such as a kneader, a Banbury mixer or a single-screwextruder, preferably in a twin-screw extruder. Thorough mixing isrequired for obtaining a very homogeneous molding material. The order inwhich the components are mixed may be varied; two or, if required, threecomponents may be premixed or all components may be mixed together.

The novel thermoplastic molding materials can be converted intomoldings, for example by injection molding or extrusion. They canfurthermore be used for the production of films or semifinished productsby the deep drawing or blow molding method.

EXAMPLE

Compositions were prepared from the following components and subjectedto performance tests:

Components A₁, A₂ and A_(v)

A₁ : Polystyrene:M_(w) =860 000 g/mol, M_(w) /M_(n) =1.7

A₂ : Polystyrene:M_(w) =1×10⁶ g/mol, M_(w) /M_(n) =1.8

A_(v) : Polystyrene:M_(w) =950 000 g/mol, M_(w) /M_(n) =4.8

Component B₁

Poly-2,6-dimethyl-1,4-phenylene ether having an average molecular weight(M_(w)) of 40 000 g/mol.

Components C₁ and C₂

C₁ : High impact polystyrene (M_(w) /M_(n) =2.4) containing 9% by weightof polybutadiene and having cellular particle morphology and a meanparticle size of the soft component of 1.9 μm. The viscosity number (VN)of the hard matrix was 80 ml/g (0.5% strength in toluene at 23° C.)

C₂ : High impact polystyrene (M_(w) /M_(n) =2.3) containing 11% byweight of polybutadiene and having cellular particle morphology and amean particle size of the soft component of 3.5 μm. The viscosity number(VN) of the hard matrix was 80 ml/g (0.5% strength in toluene at 23° C.)

Component D₁

Hydrogenated styrene/butadiene/styrene three-block copolymer (eg. SEPSblock rubber Kraton® G 1650 from Shell AG).

Components E₁ and E₂

E₁ : Triphenyl phosphate (eg. Diflamoll® TP from Bayer AG)

E₂ : Resorcinol diphosphate (eg. Fyroflex® RDP from Akzo)

Component F₁

Carbon black (eg. Black Pearls® 880 from Cabot) (as a 15% strength batchin polystyrene, M_(w) /M_(n) =2.4; viscosity number (VN) 80 ml/g, 0.5%strength in toluene at 23° C.).

Components A to F were mixed in a twin-screw extruder (ZSK 30 fromWerner & Pfleiderer) at 280° C., the mixture was extruded and theextrudate was cooled and granulated.

The dried granules were processed at from 260 to 280° C. to givecircular disks (thickness 2 mm, diameter 60 mm), flat bars (127×12.7×1.6mm) and standard small bars, and were tested.

Testing of Performance Characteristics

The damaging energy W_(s) was determined according to DIN 53 443. Forthis purpose, circular disks were penetrated at a speed of 4.6 m/s. Thedamaging energy was determined from the force-distance diagram. The meanvalue of five individual measurements is stated.

The heat distortion resistances of the samples were determined forstandard small bars according to DIN 53 460, by means of the Vicatsoftening temperature.

The notched impact strengths (a_(k)) were each determined according toISO 179 IeA.

In order to measure the flame resistances and the dripping behavior, aflame was applied to the flat bars according to UL-4294.

A flameproofed thermoplastic is classified in fire class UL-94 V0 whenthe following criteria are met:

In the case of a set of 5 samples having the dimensions 127×12.7×1.6 mm,no samples may continue burning for longer than 10 seconds afterapplication of an open flame (height 19 mm) twice for the duration of 10seconds. The sum of the subsequent combustion times in the case of 10flame applications to 5 samples must not be greater than 50 seconds.There must be no dripping of flaming particles, complete combustion orglowing for longer than 30 seconds. Classification in fire class UL 94V1 requires that the subsequent combustion times are no longer than 30seconds and that the sum of the subsequent combustion times for 10 flameapplications to 5 samples is not greater than 250 seconds. Glowing mustnot last longer than 60 seconds. The other criteria are identical tothose mentioned above. Classification in fire class UL-94 V2 is relevantwhen the additional criteria for classification UL-94 V1 are met anddripping of flaming particles occurs.

The flow behavior was investigated using a capillary rheometer at 250°C. The melt stability was determined at 320° C. by measurement in thecapillary rheometer at a measuring frequency of 55 Hz, the percentagechange in the melt viscosity in the course of 30 minutes being used as ameasure of the processing stability.

The compositions and properties of the thermoplastic molding materialsare listed in Table 1.

                  TABLE 1                                                         ______________________________________                                        Example No.                                                                            V1     V2     1    2    V3   V4   3    4                             ______________________________________                                        Component                                                                       [% by wt.]                                                                    A.sub.1 -- -- 2.5 -- -- -- 2.5 2.5                                            A.sub.2 -- -- -- 2.5 -- -- -- --                                              AV -- 2.5 -- -- -- 2.5 -- --                                                  B.sub.1 40 40 40 40 40 40 40 40                                               C.sub.1 44.7 42.2 42.2 42.2 42.7 40.2 40.2 36.2                               C.sub.2 -- -- -- -- -- -- -- 4                                                D.sub.1 3 3 3 3 3 3 3 3                                                       E.sub.1 10 10 10 10 -- -- -- --                                               E.sub.2 -- -- -- -- 11 11 11 11                                               F 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3                                             Properties                                                                    W.sub.s [Nm] 26 24 25 25 32 32 33 36                                          Vicat B 112 112 112 112 106 106 106 105                                       [° C.]                                                                 a.sub.k [kJ/m.sup.2 ] 9.1 8.9 9.0 9.2 10.3 10.0 10.6 11.5                     UL 94 V-2 V-2 V-1 V-1 V-2 V-2 V-0 V-0                                         (bars dripped) (5) (5)   (5) (5)                                              η 10 Hz 2111 2340 2176 2190 -- -- -- --                                   [Pa · s]                                                             η 100 Hz 811 864 835 830 -- -- -- --                                      [Pa · s]                                                             Δ [%] 76 93 78 79 73 96 74 76                                         ______________________________________                                         V: for comparison                                                             Δ: (η.sub.5 ' - η.sub.30 ')/n.sub.5 ' × 100 [%       

The thermoplastic molding materials which contain the novel anti-dripagents have good mechanical properties, good flow and little tendency todrip.

What is claimed is:
 1. A composition containingA) from 0.5 to 25% byweight of halogen-free antidrip agents, containing polymers based onvinylaromatic monomers having molecular weights (M_(w)) of at least800,000 g/mol and a molar mass distribution, expressed by the ratio ofweight average value M_(w) to number average value M_(n), of 2 or less,B) from 5 to 97.5% by weight of polyphenylene ether, C) from 1 to 93.5%by weight of vinylaromatic polymers which differ from those in thepolymers containing halogen-free antidrip agents, D) from 0 to 50% byweight of impact modifiers, E) from 1 to 20% by weight of flameproofingagents and F) from 0 to 60% by weight of additives or processingassistants or mixtures thereof.
 2. A composition as claimed in claim 1,containing halogen-free antidrip agents in which the vinylaromaticmonomers are styrene.
 3. A composition as claimed in claim 1, containinghalogen-free antidrip agents in which the polymers based onvinylaromatic monomers are prepared by anionic emulsion polymerization.4. A molding, film or fiber containing a composition as claimed in claim1.